Amphibians are those organisms which live on both land and in water. Bryophytes are called amphibians of the plant kingdom because these plants though live in soil but they need water for sexual reproduction. The sperm of bryophyte (antherozoids) are flagellate and need water to swim to the eggs. In other words, as these plants need water for reproduction unlike other plants, they are called as amphibians.
or in simple words they live on land but they are dependent on water to complete their sexual reproduction.